In this article I explain how to create a bootable Ubuntu usb drive.
Things you will need, a usb key with at least 2 gb of storage, an bootable Ubuntu disk image, and univeral-usb-installer which you can download here
Once you have the univeral usb installed downloaded execute it. In step 1 select the version of ubuntu you would like to install. If you have not already downloaded the ISO check the “Download the Iso” check box otherwise select the path to the iso you have chosen. Now in step 3 select the drive letter for the usb key you will be using, you can also set the amount of space to create persistent storage on the drive allowing yo to use the live usb stick as your portable Ubuntu installion, once you have done thatselect “create” and the program will format and automatically create the file system. Once done you can reboot and load your ubuntu installation.